Technical Field
The present disclosure relates to a touch sensor integrated display device and, more specifically, to a touch sensor integrated display device capable of preventing generation of a defective image between touch/common electrodes.
Discussion of the Related Art
Recently, flat panel display devices (simply referred to hereinafter as “display devices”) that are inexpensive, can increase in size and have high display quality (video expression, resolution, brightness, contrast and color reproducibility, etc.) are under development to meet demands for display devices capable of displaying multimedia with the development of multimedia. Such flat panel display devices use various input devices such as a keyboard, a mouse, a track ball, a joystick and a digitizer to constitute an interface between a user and a display device.
However, to use the aforementioned input devices, users need to learn how to use them and an additional space is required therefor, causing inconvenience and having difficulty elevating product design. Accordingly, there is increasing demand for an input device for display devices, which is convenient and simple and can reduce malfunctions. To meet such demand, a touch sensor capable of recognizing information input by a user by touching a screen of a display device with his or her hand or a pen while viewing a display device has been proposed.
The touch sensor is applied to various display devices because it is simple and rarely malfunctions and a user can apply input thereto without using an additional input device and rapidly and easily manipulate content displayed on a screen using the same.
The touch sensor used for display devices can be classified into an add-on type, an on-cell type and an integrated type or in-cell type according to structure thereof. The add-on type touch sensor is achieved by individually manufacturing a display device and a touch sensor module and then attaching the touch sensor module to an upper surface of the display device. The on-cell type touch sensor is realized by directly forming touch sensor elements on an upper glass substrate of a display device. The integrated type touch sensor is formed by integrating touch sensor elements into a display device to achieve a thin display device and improve durability.
From among the various types of touch sensors, the integrated type touch sensor is widely used because a common electrode of a display device can also be used as a touch electrode (hereinafter, the dual common and touch electrode may be referred to as a “touch and common electrode,” or alternatively, as a “touch/common electrode”) to reduce the thickness of the display device and touch elements are formed inside of the display device to improve durability.
The integrated type touch sensor attracts interest because it has durability and can realize a decrease in thickness to solve problems of the add-on type touch sensor and the on-cell type touch sensor. The integrated type touch sensor is classified into an optical type and a capacitive type according to touch point sensing method, and the capacitive type is subdivided into a self-capacitive type and a mutual capacitive type.
The self-capacitive type touch sensor includes a plurality of independent patterns formed in a touch area of a touch sensing panel and measures a capacitance variation in each independent pattern to determine whether touch is applied. In the case of the mutual capacitive type touch sensor, x-axis electrode lines (e.g., driving electrode lines) intersect y-axis electrode lines (e.g., sensing electrode lines) to form a matrix in a touch/common electrode formation area of a touch sensing panel, driving pulses are applied to the x-axis electrode lines and then voltage variations appearing at sensing nodes defined at intersections of the x-axis electrode lines and the y-axis electrode lines are sensed through the y-axis electrode lines to determine whether touch is applied. As used herein, the term “intersect” does not require physical connection between intersecting lines, but instead may be used to describe a relationship where one line crosses over another line.
In the mutual capacitive type touch sensor, however, mutual capacitance generated during touch sensing is very small whereas parasitic capacitance between a gate line and a data line constituting a display device is very large, and thus it is difficult to correctly detect a touch point due to the parasitic capacitance.
Furthermore, the mutual capacitive type touch sensor requires a very complicated wiring structure because a plurality of touch driving lines for touch driving and a plurality of touch sensing lines for touch sensing need to be formed on common electrodes for multi-touch recognition.
The self-capacitive type touch sensor can improve touch accuracy with a simple wiring structure compared to the mutual capacitive type touch sensor and thus is widely used.
A description will be given of a self-capacitive type touch sensor integrated LCD (referred to as “touch sensor integrated display device” hereinafter) of the related art with reference to FIGS. 1 to 3.
FIG. 1 is a plan view schematically illustrating the touch sensor integrated display device of the related art. FIG. 2 is a plan view of a region R1 shown in FIG. 1. FIG. 3 is a waveform diagram illustrating a common voltage coupling effect of touch/common electrodes according to gate signals supplied to gate lines overlapping with touch/common electrodes in a row and touch/common electrodes in the next row.
The touch sensor integrated display device includes an active area AA in which touch/common electrodes and pixel electrodes are arranged and data is displayed, and a bezel area BA outside the active area AA and including various wires and touch controllers ICs arranged therein.
The active area AA includes a plurality of touch/common electrodes T11 to T8a arranged in a first direction (e.g., x-axis direction) and a second direction (e.g., y-axis direction) perpendicular to each other, and a plurality of touch/common lines (which may alternatively be referred to herein as “touch and common lines”) W11 to W8a arranged in parallel in the second direction to connect the plurality of touch/common electrodes T11 to T8a to a touch controller 10.
The plurality of touch/common electrodes T11 to T8a arranged in the active area AA are formed in such a manner that common electrodes of a previous display device are divided, operate as common electrodes in a display mode of displaying data and operate as touch electrodes in a touch mode of detecting a touch point.
Referring to FIG. 2, in the touch sensor integrated display device of the related art, a plurality of pixel electrodes (not shown) is arranged corresponding to a single touch/common electrode T11, for example. The plurality of pixel electrodes is arranged in an area defined by intersections of gate lines G11 to G2c and data lines D1 to D18. In the example shown in FIG. 2, 108 pixel electrodes are arranged corresponding to one touch/common electrode T11 in an area defined by 12 gate lines G11 to G1c and 9 data lines D1 to D9 intersecting the gate lines G11 to G1c. 
Touch/common electrodes T11, T12, T21 and T23 are provided with a common voltage through touch/common lines W11, W12, W21 and W22 in a display driving period and are provided with a touch driving voltage in a touch driving period. The touch/common lines W11, W12, W21 and W22 provide a touch sensing voltage sensed from the touch/common electrodes T11, T12, T21 and T23 to the touch controller 10 in the touch driving period. The touch controller 10 determines whether touch is applied and a touch point using a known touch algorithm.
Referring to FIG. 3, when gate signals are sequentially provided to (1-1)th to (1-c)th gate lines G11 to G1c corresponding to the touch/common electrodes T11 to T1a arranged in the first row, coupling is generated in touch/common electrodes T11 to T1a and T21 to T2a due to on/off voltages of the gate signals supplied to the gate lines and thus ripple voltages are generated at a rising edge and a falling edge of each gate signal.
The ripple voltages are generated when a gate signal is supplied to each gate line but are offset by a subsequent gate signal. For example, ripple voltages of the touch/common electrodes T11 to T1a due to a falling edge of the gate signal supplied to the (1-6)th gate line G16 are offset by ripple voltages of the touch/common electrodes T11 to T1a due to a rising edge of the gate signal supplied to the (1-9)th gate line G19, ripple voltages of the touch/common electrodes T11 to T1a due to the (1-7)th gate line G17 are offset by ripple voltages of the touch/common electrodes T11 to T1a due to the (1-10)th gate line G1a, ripple voltages of the touch/common electrodes T11 to T1a due to the (1-8)th gate line G18 are offset by ripple voltages of the touch/common electrodes T11 to T1a due to the (1-11)th gate line G1b, and ripple voltages of the touch/common electrodes T11 to T1a due to the (1-9)th gate line G19 are offset by ripple voltages of the touch/common electrodes T11 to T1a due to the (1-12)th gate line G1c. 
However, the ripple voltages of the touch/common electrodes T11 to T1a due to falling edges of the gate signals supplied to the (1-10)th to (1-12)th gate lines G1a to G1c are not offset because the (2-1)th gate line G21 and the (2-2)th gate line G22 are arranged to correspond to touch/common electrodes T21 to T2a arranged in the second row.
Accordingly, a common voltage level becomes unstable due to a ripple voltage level difference between the touch/common electrodes arranged in the same row and boundaries thereof, causing a defective image in the form of a bright horizontal line according to common voltage value variation in the touch sensor integrated display device of the related art.